7. Masonry. This is one that bridges all four factors — if there is a structural component to the masonry project (and there usually is), safety is a concern. The scale of projects involving stone, brick and concrete can be deceiving. Make sure you know what you're getting into. Wrestling a heavy stone into place and making it look good takes years to master. When you factor in all of this, the cost of paying for good work can be a bargain.
6. Carpentry. Even if you have the skills to complete the project, professional carpenters will have the tools and experience to get the job done quickly. If you are trying to complete the project on a part-time basis, remember to factor in setup and cleanup time. Working a full day is often much more efficient than an hour here and there.